Syringe

ABSTRACT

A retractable needle safety syringe is provided having mitigated retraction. The syringe comprises a syringe body, a syringe cavity, a plunger, a variable vacuum compartment, a shaft brake, and a ram member. The plunger assembly includes a plunger shaft and a piston slidably engaged within the syringe body. The variable vacuum compartment is disposed within the syringe cavity and provides a vacuum force on the plunger shaft directed from a bottom syringe body end toward a top syringe body end. The shaft brake, being attached to the top syringe body end, may frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted prior to the piston reaching the bottom syringe body end, the second frictional force being exerted in response to the engagement of the ram member with the shaft brake.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/679,113 entitled “IMPROVED SYRINGE” filed May 9, 2005, the entirety of the disclosure of which is expressly incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The risks associated with the spread of blood-borne pathogens through use of hypodermic needles are significant and well documented. In recent years, the public has become increasingly aware of the health hazards associated with needle reuse and accidental needle prickings. These risks are most prevalent among certain groups of people, such as drug addicts, drug users (e.g., diabetics), medical personnel and healthcare providers. In fact, more than twenty blood-borne pathogens can be transmitted by the reuse of needles or accidental needle prickings, just a few of which include human immunodeficiency virus (HIV), acquired immunodeficiency syndrome (AIDS), hepatitis B, hepatitis C, syphilis, malaria, tuberculosis, and herpes.

In 1997, the Centers for Disease Control and Prevention (CDC) sponsored a study which found that approximately 76% of needle pricking injuries could be avoided by using safety needles. As a result, needle legislation has now been introduced in approximately twenty-five states and in the District of Columbia. In fact, such safety needle legislation has already been signed into law in a number of states including California, Texas, Tennessee, New Jersey and Maryland. In addition, the Occupational Safety and Health Administration (OSHA) has promulgated a Blood-borne Pathogens Standard requiring employers to evaluate the effectiveness of existing controls designed to minimize or eliminate employee occupational exposure and to review the feasibility of instituting more advanced controls. Furthermore, the Food and Drug Administration (FDA), in an effort to protect health care workers, has set forth guidelines suggesting specific features that a safety syringe should possess. These include a safety feature that is not only simple and self evident to operate, thus requiring little or no additional training to use effectively, but also a safety feature that is an integral part of the apparatus. In other words, the guidelines suggest that the safety feature itself be unremovable and utilization of the safety feature be unavoidable. (www.osha-slc.gov/SLTC/needle stick/saferneedledevices/saferneedledevices.html; www.seiu.org).

As a result of the foregoing state legislation and agency guidelines, a great amount of time, effort and money has been invested by syringe manufacturers in developing syringes with safety needle designs. Presently, there are at least 250 types of safety syringes. However, the safety syringes that currently exist have been criticized for generally being too expensive to manufacture and having a safety feature that is not an integral part of the safety syringe. Another criticism includes safety syringes that are not economically feasible because operation of the safety feature is not self evident and therefore additional training is required to use the apparatus effectively. Additionally, the safety feature of at least one safety syringe is simply ineffective at preventing the transmission of blood-borne pathogens due to “reflux” blood contamination.

Of the current safety syringes, safety syringes using a spring mechanism are the most common for automatically retracting a hollow needle after injecting a fluid. However, these safety syringes are typically more expensive because of the required incorporation of additional materials for manufacture. Standard or conventional hypodermic needle syringes typically cost from five to seven cents each. On the other hand, the median increase in cost for a safety syringe is approximately thirty cents or more. At first glance, this minimal cost increase does not seem significant. However, after considering the thousands, if not millions, of needles used each year, the resultant increase in annual cost for utilizing the more expensive safety syringe is unfortunately excessive.

Another syringe has been created that avoids some of the additional cost associated with spring mechanism safety syringes. This syringe, found in U.S. Pat. No. 6,413,236, entitled “Automatically Retractable Needle Safety Syringe,” issued on Jul. 2, 2002, seeks to solve the problem of needle reuse and accidental needle prickings through use of a vacuum. As disclosed therein, the safety syringe is configured to automatically retract the needle portion of the syringe into the body of the syringe utilizing a vacuum within the syringe, such that after a single use, the syringe may not be reusable nor lead to an accidental pricking.

As understood, the syringe of U.S. Pat. No. 6,413,236 utilizes vacuum pressure to exert an automatic retracting force upon the needle. Apparently, the syringe includes a plunger and a needle body (to which the needle is attached) and is configured to frictionally engage the plunger with the needle body. Once engaged with the needle body, the vacuum pressure inside the syringe exerts the retracting force upon the plunger, which causes the plunger to remove the needle body and pull it into the syringe itself. After being completely retracted, the needle does not protrude and the syringe cannot be reused nor accidentally prick an individual.

The aforementioned retractable safety syringes have helped alleviate many of the problems associated with accidental needle prickings and reuse of hypodermic needles. However, due to the configuration and retraction force inherent in the vacuum or spring mechanism aspect of these syringes and others like them, the user of the syringe may often experience difficulties in its use. Specifically, due to the vacuum pressure or spring mechanism, which exerts an automatic retracting force upon the plunger, the plunger may automatically retract at an undesirable time.

It is an apparent object of these syringes to retract the plunger when the needle body has been frictionally engaged with the plunger. However, automatic retraction of the plunger prior to frictional engagement with the needle body may often be very problematic. For example, automatic retraction may make syringe handling very difficult between the time the fluid is drawn to the time the fluid is emptied. In effect, a user must manually maintain the position of the plunger by exerting a force to counter the automatic retracting force. Otherwise, the plunger will retract. Retraction of the plunger may be a nuisance if the syringe has not been introduced into the subject. However, while the needle is introduced into the subject, retraction of the plunger could effectively result in drawing fluid therefrom instead of the intended injection of fluid into the subject. This situation could be very harmful and lead to various unfortunate consequences.

Therefore, a need exists for an effective and efficient, inexpensive safety syringe that is simple and self evident to operate and integrally comprises a safety feature having a hollow needle that protectively retracts automatically after a single injection, but that mitigates against automatic retraction of the needle prior to completion of use. Further, there is a need in the art for an automatically retractable safety syringe that mitigates against automatic retraction of the needle during administration of the fluid injected therewith.

BRIEF SUMMARY OF THE INVENTION

In accordance with an embodiment of the present invention, a retractable needle safety syringe is provided with mitigated retraction. The syringe comprises a syringe body defining opposing top and bottom syringe body ends and including a syringe cavity; an attachment seal defining a shaft orifice and being attached to the top syringe body end; a plunger assembly including a plunger shaft and a piston, the plunger shaft defining opposing top and bottom shaft ends, the plunger shaft being disposed through the shaft orifice in the syringe cavity, the piston being disposed at the bottom shaft end, the plunger being slidably engaged with the syringe body within the syringe cavity; a variable vacuum compartment being disposed within the syringe cavity between the piston and the attachment seal, the variable vacuum compartment being operative to provide a vacuum force on the plunger shaft directed from the bottom syringe body end toward the top syringe body end with the vacuum force increasing upon movement of the piston toward the bottom syringe body end; a shaft brake being attached to the top syringe body end and being operative to frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted upon the plunger shaft prior to the piston reaching the bottom syringe body end; and a ram member being attached to the top shaft end and being formed to engage the shaft brake upon the piston reaching the bottom syringe body end, the shaft brake exerting the second frictional force upon the plunger shaft in response to the engagement of the ram member with the shaft brake, the second frictional force being less than the first frictional force.

The first frictional force may have an associated first normal force. The second frictional force may have an associated second normal force. Additionally, the shaft brake substantially disengages from the plunger shaft upon engagement of the ram member with the shaft brake.

The shaft brake may define a body perimeter and include an aperture and a bridge, the aperture being disposed within the shaft brake and frictionally engaging the plunger shaft, the bridge defining a bridge width and extending radially from the aperture toward the body perimeter, the shaft brake being operative to exert the second frictional force upon the plunger shaft in response to an increase in bridge width, the bridge width increasing in response to the engagement of the ram member with the shaft brake. The ram member may at least partially sever the bridge to increase the bridge width.

The shaft brake may further include a release member being disposed upon the shaft brake, the bridge width increasing in response to the engagement of the ram member with the release member. The release member may be a shoulder protruding upwardly from the shaft brake opposite the syringe body, and the ram member includes a shoulder press being sized and configured to engage the shoulder upon the piston approaching the bottom syringe body end, the bridge width increasing in response to the engagement of the shoulder press with the shoulder. The bridge width may increase upon deformation of the bridge in response to engagement of the shoulder press with the shoulder and continued movement of the piston toward the bottom syringe body end.

The brake body may define a body thickness and the bridge may define a bridge thickness, the bridge thickness being less than the body thickness, the bridge being operative to deform in response to the engagement of the shoulder press with the shoulder. The bridge may comprise a non-continuous slit including a hinge element, and the bridge width may increase upon deformation of the hinge element in response to engagement of the shoulder press with the shoulder and continued movement of the piston toward the bottom syringe body end.

The shaft brake may be formed to include an anchor member being disposed upon the shaft brake, the anchor member being operative to mechanically couple the shaft brake to the attachment seal. The syringe may further include a needle being removably mounted to the bottom syringe body end and extending therefrom opposite the top syringe body end, the piston including a punch to engage the needle upon the piston reaching the bottom syringe body end, the piston being operative to remove the needle into the syringe cavity upon exertion of the vacuum force upon the plunger shaft.

In accordance with another embodiment of the present invention, a method is provided of mitigating retraction of a retractable needle safety syringe. The syringe comprises a syringe body, an attachment seal, a plunger assembly, a variable vacuum compartment, a shaft brake, and a ram member, the syringe body defining opposing top and bottom syringe body ends and including a syringe cavity, the attachment seal defining a shaft orifice and being attached to the top syringe body end, the plunger assembly including a plunger shaft and a piston, the plunger shaft defining opposing top and bottom shaft ends, the plunger shaft being disposed through the shaft orifice in the syringe cavity, the piston being disposed at the bottom shaft end, the plunger being slidably engaged with the syringe body within the syringe cavity, the variable vacuum compartment being disposed within the syringe cavity between the piston and the attachment seal, the variable vacuum compartment being operative to provide a vacuum force on the plunger shaft directed from the bottom syringe body end toward the top syringe body end with the vacuum force increasing upon movement of the piston toward the bottom syringe body end, the shaft brake being attached to the top syringe body end and being operative to frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted upon the plunger shaft prior to the piston reaching the bottom syringe body end, the ram member being attached to the top shaft end and being formed to engage the shaft brake upon the piston reaching the bottom syringe body end, the shaft brake exerting the second frictional force upon the plunger shaft in response to the engagement of the ram member with the shaft brake, the second frictional force being less than the first frictional force. The method comprises: (a) exerting the first frictional force upon the plunger shaft in opposition to the vacuum force prior to the piston reaching the bottom syringe body end; (b) engaging the ram member with the shaft brake; and (c) exerting the second frictional force upon the plunger shaft in opposition to the vacuum force in response to the engagement of the ram member with the shaft brake.

According to another implementation of the method, the shaft brake defines a body perimeter and includes an aperture and a bridge, the aperture being disposed within the shaft brake and being operative to frictionally engage the plunger shaft, the bridge defining a bridge width and extending radially from the aperture toward the body perimeter, the shaft brake being operative to exert the second frictional force upon the plunger shaft in response to an increase in bridge width, the bridge width increasing in response to the engagement of the ram member with the shaft brake, and step (b) of the method may further include: increasing the bridge width in response to the engagement of the ram member with the shaft brake.

In accordance with yet another implementation of the method, step (b) may further include: severing the bridge in response to the engagement of the ram member with the shaft brake.

In accordance with yet another implementation of the method, the shaft brake further includes a shoulder being disposed upon the shaft brake and protruding upwardly from the shaft brake opposite the syringe body, and the ram member includes a shoulder press being sized and configured to engage the shoulder upon the piston approaching the bottom syringe body end, the bridge width increasing in response to the engagement of the shoulder press with the shoulder, and step (b) of the method may further include: engaging the shoulder press with the shoulder; and deforming the bridge to increase the bridge width.

In accordance with yet another implementation of the method, the syringe further includes a needle being removably mounted to the bottom syringe body end and extending therefrom opposite the top syringe body end, the piston including a punch to engage the needle upon the piston reaching the bottom syringe body end, the piston being operative to remove the needle into the syringe cavity upon exertion of the vacuum force upon the plunger shaft, and the method may further include the steps of: engaging the needle with the punch; and automatically removing the needle into the syringe cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

An illustrative and presently preferred embodiment of the invention is shown in the accompanying drawings in which:

FIG. 1 a cross sectional view of a retractable needle safety syringe with mitigated retraction in accordance with an aspect of the present invention;

FIG. 2 is a cross sectional view of the syringe illustrating the interaction between a ram member and a shaft brake;

FIG. 3 is a top plan view of the shaft brake in accordance with another embodiment of the present invention;

FIG. 4 is a side view of the shaft brake in accordance with another embodiment of the present invention; and

FIG. 5 is a top plan view of the shaft brake in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiments of the present invention only and not for purposes of limiting the same, FIG. 1 is a cross sectional view of a retractable needle safety syringe 10 with mitigated retraction in accordance with an aspect of the present invention.

An embodiment of the syringe comprises a syringe body 12, an attachment seal 14, a plunger assembly 16, a variable vacuum compartment 18, a shaft brake 20, and a ram member 22. The syringe body 12 defines opposing top and bottom syringe body ends 24, 26 and includes a syringe cavity 28. The attachment seal 14 defines a shaft orifice 30 and is attached to the top syringe body end 24. The plunger assembly 16 includes a plunger shaft 32 and a piston 34. The plunger shaft 32 defines opposing top and bottom shaft ends 36, 38. The plunger shaft 32 is disposed throughout the shaft orifice 30 in the syringe cavity 28. The piston 34 is disposed at the bottom shaft end 38. The plunger is slidably engaged with the syringe body 12 within the syringe cavity 28. The variable vacuum compartment 18 is disposed within the syringe cavity 28 between the piston 34 and the attachment seal 14. The variable vacuum compartment 18 is operative to provide a vacuum force 40 on the plunger shaft 32 directed from the bottom syringe body end 26 toward the top syringe body end 24 with the vacuum force 40 increasing upon movement of the piston 34 toward the bottom syringe body end 26. The shaft brake 20 is attached to the top syringe body end 24 and is operative to frictionally engage the plunger shaft 32 to provide first and second frictional forces 42, 44 in opposition to the vacuum force 40. The first frictional force 42 is exerted upon the plunger shaft 32 prior to the piston 34 reaching the bottom syringe body end 26. The ram member 22 is attached to the top shaft end 36 and is formed to engage the shaft brake 20 upon the piston 34 reaching the bottom syringe body end 26. The shaft brake 20 exerts the second frictional force 44 upon the plunger shaft 32 in response to the engagement of the ram member 22 with the shaft brake 20. The second frictional force 44 is less than the first frictional force 42.

As illustrated in FIG. 1, the syringe may further include a needle 46 being removably mounted to the bottom syringe body end 26 and extending therefrom opposite the top syringe body end 24. The piston 34 may include a punch 48 to engage the needle 46 upon the piston 34 reaching the bottom syringe body end 26. The piston 34 may be operative to remove the needle 46 into the syringe cavity 28 upon exertion of the vacuum force 40 upon the plunger shaft 32. The needle 46 may be attached to the bottom syringe body end 26 via a needle body 50. The punch 48 may engage the needle body 50 of the needle 46 upon the piston 34 reaching the bottom syringe body end 26.

As will be appreciated by one of skill in the art, in order to effectuate an intake of fluid into the syringe cavity 28 of the syringe body 12, a thumb platform 52 of the plunger should first be depressed by thrusting the thumb platform 52 toward the syringe body 12 to remove a majority of the air present within the syringe cavity 28 between the bottom syringe body end 26 and the piston 34. During this depression, the piston 34 of the plunger assembly 16 is forced to slide within the syringe cavity 28 toward the bottom syringe body end 26. The attachment seal 14 and the piston 34 are substantially air tight and fluid tight. Therefore, a corresponding influx of air molecules and fluid molecules into the variable vacuum compartment 18 of the syringe body 12 is prevented. As a result, the volume within the variable vacuum compartment 18 is increased without a corresponding influx of air molecules or fluid molecules therefore creating a vacuum within the variable vacuum compartment 18. In order to complete the intake of fluid into the syringe cavity 28, while the thumb platform 52 remains forcibly depressed, a piercing tip end 54 of the needle 46 is submerged into a fluid present within a fluid container. Once the piercing tip end 54 is submerged within the fluid, the thumb platform 52 is allowed to move, as a result of the vacuum created within the variable vacuum compartment 18 and a decrease in the forcible depression, away from the syringe body 12 thus effectuating a withdraw of a desired amount of fluid from a fluid container into the syringe cavity 28.

In order to inject the fluid and retract the needle 46 into the syringe body 12, the operation of the syringe may be as follows. The piercing tip of the needle 46 may be inserted into a patient or other instrument wherein the fluid is to be injected. Upon depressing the thumb platform 52, the fluid may be evacuated from the syringe cavity 28 and injected. During this injection stroke, a vacuum may be created within the variable vacuum compartment 18 as a result of an increase in volume within the variable vacuum compartment 18 without a corresponding influx of air molecules due to the attachment seal 14 and the piston 34 creating an air tight and fluid tight seal, as mentioned above. At the end of the injection stroke, as the piston 34 reaches the bottom syringe body end 26, the punch 48 may frictionally engage the needle body 50. Due to the vacuum force 40, the needle 46 may immediately and automatically be withdrawn within the syringe cavity 28 such that the entire needle 46 permanently resides enclosed within and protectively pressed against the syringe cavity 28. This alleviates needle 46 reuse and accidental needle 46 prickings and, therefore, ultimately prevents the transmission of blood born pathogens and other diseases by contaminated syringe needles 46.

As mentioned above, when the variable vacuum compartment 18 is enlarged upon movement of the piston 34 toward the bottom syringe body end 26, the vacuum created within the variable vacuum compartment 18 may exert a vacuum force 40 upon the plunger shaft 32. As will be understood by one of skill, the vacuum force 40 may be exerted upon the plunger shaft 32 indirectly via exertion upon the piston 34. The vacuum force 40 may vary as the piston 34 moves toward the bottom syringe body end 26 or toward the top syringe body end 24. Thus, the vacuum force 40 may increase or decrease, respectively. The vacuum force 40 may be exerted on the plunger shaft 32 directed from the bottom syringe body end 26 toward the top syringe body end 24. The vacuum force 40, as disclosed in an embodiment of the present invention, may be caused due to a vacuum pressure in the variable vacuum compartment 18. However, in accordance with another aspect of the present invention, the vacuum force 40 may also be produced due to a spring mechanism that is housed in the variable vacuum compartment 18. The vacuum force 40 therefore need not be produced only due to the vacuum within the variable vacuum compartment 18. In this regard, it is also contemplated that the variable vacuum compartment 18 need not be air tight when such a spring mechanism is used therein to produce the vacuum force 40.

According to an aspect of the present invention, the shaft brake 20 is attached to the top syringe body end 24 and is operative to frictionally engage the plunger shaft 32 to provide the first frictional force 42 in opposition to the vacuum force 40. The first frictional force 42 may be exerted upon the plunger shaft 32 prior to the piston 34 reaching the bottom syringe body end 26. Nevertheless, in accordance with an aspect of the present invention, the first frictional force 42 may be exerted upon the plunger shaft 32 even after the piston 34 has reached the bottom syringe body end 26. For example, as mentioned above, in order to intake fluid in preparation for an injection, the first frictional force 42 may be continuously exerted upon the piston 34 shaft as the piston 34 moves toward and away from the bottom syringe body end 26. In this regard, the first frictional force 42 exerted upon the plunger shaft 32 may be equivalent to or greater than the vacuum force 40. This advantageous embodiment of the present invention may provide that the user need not maintain continuous forcible depression of the thumb platform 52 after intaking fluid in preparation for the injection. Otherwise, the vacuum force 40 exerted upon the plunger shaft 32 would require the user to either maintain the thumb platform 52 being depressed or intake air into the syringe cavity 28. An even more troublesome situation may resolved with an embodiment of the present invention. If the user does not maintain the forcible depression of the thumb platform 52 after injection and prior to withdrawal of the piercing tip end 54 from the patient or instrument, the vacuum force 40 may cause intake of fluids from the patient or instrument. Risks associated with this type of accident may be alleviated by implementing aspects of the present invention. As discussed above, continuous exertion of the first frictional force 42 by the shaft brake 20 upon the plunger shaft 32 may counteract the vacuum force 40 and help avoid such difficulties of syringe use. Overall, equalization of the vacuum force 40 by the first frictional force 42 may provide the user with greater control over intake and injection using the syringe.

In accordance with an aspect of the present invention, the ram member 22 is attached to the top shaft end 36 and is formed to engage the shaft brake 20 upon the piston 34 reaching the bottom syringe body end 26. As illustrated in FIGS. 1 and 2, the ram member 22 may be integrally formed with the thumb platform 52. Nevertheless, the ram member 22 may be attached and configured as required in order to provide optimal mechanical engagement with the shaft brake 20. The engagement of the ram member 22 with the shaft brake 20 is therefore contemplated to be primarily a mechanical engagement as shown in FIG. 2. As such, the mechanical engagement contemplated herein may likely provide a cost effective, efficient and safe means for releasing the shaft brake 20. It is nevertheless contemplated that the engagement of the ram member 22 with the shaft brake 20 may be indirect through other elements, or that the engagement may be other than mechanical, such as electrical or chemical. Further, although an embodiment of the ram member 22 is illustrated herein, the shaft brake 20 may be variously modified.

Upon engagement of the ram member 22 with the shaft brake 20, the shaft brake 20 may exert the second frictional force 44 upon the plunger shaft 32. As discussed above, it is contemplated that the first frictional force 42 may be exerted by the shaft brake 20 upon the plunger shaft 32 upon the piston 34 moving toward and away from the bottom syringe body end 26. Thus, although the piston 34 may approach the bottom syringe body end 26, engagement may not occur. For example, in an embodiment, the ram member 22 may be configured to engage the shaft brake 20 only upon the piston 34 being thrusted to the bottom syringe body end 26. In this regard, it is contemplated that the ram member 22 and the shaft brake 20 may contact each other prior to engagement of the piston 34 with the shaft brake 20. The engagement process, as contemplated in one embodiment of the present invention, is depicted in FIG. 2. As shown therein, the continued movement of the plunger assembly 16 toward the bottom syringe body end 26 may be operative to cause complete engagement of the ram member 22 with the shaft brake 20. Certain other advantageous features may also be incorporated into embodiments of the present invention such as prophylactic measures to prevent premature engagement. For example, after making the initial contact, the user may be aware that further displacement of the piston 34 toward the bottom syringe body end 26 will result in engagement of the ram member 22 with the shaft brake 20, which may be accomplished through sound, feel, or other possible indications from the syringe. Such a prophylactic measure may allow the user to control the engagement of the ram member 22 with the shaft brake 20, which in turn may coincide with the engagement of the punch 48 with the needle 46 and retraction of the needle 46 into the syringe cavity 28. Therefore, various designs may be incorporated into aspects of the present invention to ensure that deliberate engagement and retraction take place.

Upon engagement of the ram member 22 with the shaft brake 20, the shaft brake 20 may exert the second frictional force 44 upon the plunger shaft 32. According to an aspect of the present invention, the second frictional force 44 may be less than the first frictional force 42. As discussed above, while the first frictional force 42 may be equivalent to or greater than the vacuum force 40, it is contemplated that the second frictional force 44 may be less than the vacuum force 40. Therefore, in operation after the injection stroke, the ram member 22 may engage the shaft brake 20, and simultaneously, the syringe may be configured to engage the punch 48 with the needle 46. Then, due to the engagement of the ram member 22 with the shaft brake 20, the first frictional force 42 may be replaced by the second frictional force 44, which may be less than the vacuum force 40, resulting in substantially unrestrained retraction of the needle 46 into the syringe cavity 28.

The first frictional force 42 may have an associated first normal force 56. The first normal force 56 may therefore be directly related to the configuration and placement of the shaft brake 20 about the plunger shaft 32, the pressure exerted thereon being the first normal force 56. The first normal force 56 may be increased or decreased according to design requirements. As may be appreciated by one of skill in the art, the shaft brake 20 and the first normal force 56 exerted by the shaft brake 20 upon the plunger shaft 32, may be configured according to user requirements. As is known in the art, the first frictional force 42 (F_(first)) may be represented mathematically as: F_(first)=μ_(k/s)N_(first), where μ_(k/s) represents the coefficient of kinetic/sliding friction, and N_(first) represents the first normal force 56. The first normal force 56 may be exerted in certain embodiments, with the shaft brake 20 entirely encircling and contacting the plunger shaft 32 about the entire circumference of the plunger shaft 32. However, in alternative embodiments, it is contemplated that the first normal force 56 may be exerted by the shaft brake 20 by contacting only a portion of the circumference of the plunger shaft 32.

The second frictional force 44 may have an associated second normal force 58. Similar to that shown above, the second frictional force 44 may be calculated using the equation; F_(second)=μ_(k/s)N_(second). The shaft brake 20 may be at least partially released from the plunger shaft 32 upon engagement of the ram member 22 with the shaft brake 20 and thus exert the second frictional force 44, which may be greater than or equal to zero. In such circumstances where the shaft brake 20 is not completely disengaged from the plunger shaft 32, the second normal force 58 may likely be greater than zero, but it is contemplated that the second normal force 58 may most frequently be less than the first normal force 56. For example, where the shaft brake 20 substantially disengages from the plunger shaft 32, the second normal force 58 may be less than or negligible relative to the first normal force 56, but may be greater than zero.

According to an aspect of the present invention, it is contemplated that the shaft brake 20 and the plunger shaft 32 may be fabricated from various materials. In this regard, the coefficients of static and kinetic friction may vary depending on the material from which the shaft brake 20 and the plunger shaft 32 are fabricated. As discussed above, it is contemplated that the first frictional force 42 may be equivalent to or greater than the vacuum force 40 during intake of fluid into the syringe. As will be appreciated by one of skill in the art, a suitable material may be selected based upon its coefficient of static friction and its coefficient of kinetic friction in order to facilitate use of the syringe such as allowing the user to not be required to maintain depression of the thumb platform 52 during the intake operation. Other considerations and requirements may also be addressed by manipulating the characteristics of various materials and their frictional properties as is known in the art.

Referring now to FIG. 3, the shaft brake 20 may define a body perimeter 60 and include an aperture 62 and a bridge 64. The body perimeter 60 may be generally defined as the outer most portion of the shaft brake 20. The aperture 62 may be disposed within the shaft brake 20 and frictionally engage the plunger shaft 32. The bridge 64 may define a bridge width 66 and extend radially from the aperture 62 toward the body perimeter 60. The shaft brake 20 may be operative to exert the second frictional force 44 upon the plunger shaft 32 in response to an increase in bridge width 66, the bridge width 66 increasing in response to the engagement of the ram member 22 with the shaft brake 20. It is contemplated that prior to the increase in bridge width 66, the shaft brake 20 may exert the first frictional force 42 upon the plunger shaft 32, as discussed above.

In an embodiment of the present invention, the increase in bridge width 66 may directly or indirectly cause a corresponding increase in the size of the aperture 62 of the shaft brake 20. With an increase of the size of the aperture 62, the plunger shaft 32 may therefore be disengaged from the aperture 62, and correspondingly from the shaft brake 20, as discussed above. In situations where the aperture 62 increases dramatically in size, as mentioned previously, the second frictional force 44 may be negligible or approximately zero. However, where the increase in bridge width 66 is minimal, and results in a corresponding minimal increase in the size of the aperture 62, the second frictional force 44 may be at most less than either the first frictional force 42 or the vacuum force 40. It is contemplated that the bridge width 66 may increase due to deformation of the bridge 64 of the shaft brake 20. This deformation may therefore allow the shaft brake 20 to disengage from the plunger shaft 32 and exert the second frictional force 44 upon the plunger shaft 32. The deformation of the bridge 64 may be permanent or elastic. In use, it is contemplated that the deformation need only be permanent until the needle 46 is fully retracted into the syringe cavity 28. Thus, the shaft brake 20 may be fabricated from a material that experiences prolonged plastic deformation. In addition, the ram member 22 may at least partially sever the bridge 64 in order to increase the bridge width 66. Thus, the bridge 64 may experience a permanent or temporary change in its physical structure in order to provide an increase in the bridge width 66 in response to engagement of the ram member 22 with the shaft brake 20.

The shaft brake 20 may further include a release member 68 being disposed upon the shaft brake 20, as illustrated in FIGS. 1 and 2. The bridge width 66 may increase in response to engagement of the ram member 22 with the release member 68. Although illustratively shown in FIGS. 1 and 2, the release member 68 may be configured in various ways, as dictated by design requirements. For example, as mentioned above, the ram member 22 may be operative to deform or to sever the bridge 64 of the shaft brake 20, which may be done directly or indirectly. Thus, depending on the design, the ram member 22 may engage the release member 68 and effectuate an increase in the bridge width 66. As illustratively shown in FIGS. 1 and 2, the release member 68 may be a shoulder 70 protruding upwardly from the shaft brake 20 opposite the syringe body 12, and the ram member 22 may include a shoulder press 72 being sized and configured to engage the shoulder 70 upon the piston 34 approaching the bottom syringe body end 26, the bridge width 66 increasing in response to the engagement of the shoulder press 72 with the shoulder 70. The engagement of the shoulder press 72 with the shoulder 70 may be done as illustrated in FIG. 2, with the shoulder press 72 being oriented at an angle relative to the thumb platform 52, and the shoulder 70 being configured to substantially mate with the shoulder press 72. Other various designs and configurations may also be implemented.

The bridge width 66 may increase upon deformation of the bridge 64 in response to engagement of the shoulder press 72 with the shoulder 70 and continued movement of the piston 34 toward the bottom syringe body end 26. Therefore, as discussed above, the syringe may include a contact position whereat the user may know that further displacement of the piston 34 toward the bottom syringe body end 26 will result in engagement of the ram member 22 or shoulder press 72 with the shaft brake 20 or shoulder 70. Upon further displacement then, the shaft brake 20 may exert the second frictional force 44 upon the plunger shaft 32. This may be accomplished by increasing the bridge width 66.

The shaft brake 20 may be configured to various embodiments in order to increase the bridge width 66 in response to engagement of the ram member 22 with the shaft brake 20. For example, the brake body may define a body thickness 74 and the bridge 64 may define a bridge thickness 76, as shown in FIG. 4. The bridge thickness 76 may be less than the body thickness 74, and the bridge 64 may be operative to deform in response to the engagement of the shoulder press 72 with the shoulder 70. Thus, upon engagement of the ram member 22 with the shaft brake 20, the ram member 22 may be configured to produce a deformation in the shaft brake 20. Thus, if the ram member 22 produces a tensile force through the shaft brake 20, having the bridge thickness 76 less than the body thickness 74 may result in deformation along the bridge 64 and subsequent increase in the bridge width 66, which then triggers exertion of the second frictional force 44 upon the plunger shaft 32. In other embodiments, the bridge thickness 76 may be less than the body thickness 74 by allowing the bridge 64 to comprise a slit and a laminated material extending across the slit. The laminate material may have a lesser tensile strength than the shaft brake 20, and therefore, as described previously, deform upon exertion of a tensile force by the ram member 22 upon the shaft brake 20. This deformation would likewise result in an increase in the bridge width 66 and subsequent exertion of the second frictional force 44 upon the plunger shaft 32. Other embodiments and designs may be employed to create desirable results.

As shown in an exemplary embodiment illustrated in FIG. 5, in another implementation of the present invention, the bridge 64 may comprise a non-continuous slit 78 including a hinge element 80, and the bridge width 66 increases upon deformation of the hinge element 80 in response to engagement of the shoulder press 72 with the shoulder 70 and continued movement of the piston 34 toward the bottom syringe body end 26. Thus, instead of varying the bridge thickness 76 relative to the body thickness 74, the bridge width 66 may simply vary relative to the brake body. In such an embodiment, modifications such as this would result in deformation of the bridge 64 and a resulting increase in the bridge width 66 upon engagement of the ram member 22 and exertion of a tensile force across the shaft brake 20.

The shaft brake 20 may be formed to include an anchor member 82 being disposed upon the shaft brake 20, as shown in FIGS. 1, 2 and 4. The anchor member 82 may be operative to mechanically couple the shaft brake 20 to the attachment seal 14, as shown in FIGS. 1 and 2. However, it is contemplated that the anchor member 82 may provide other various advantages for the shaft brake 20, other than simple mechanical coupling to the attachment seal 14. For example, it is contemplated that the anchor member 82 be operative to provide at least a portion of the first and second frictional forces 44 upon the plunger shaft 32. In such an embodiment, the anchor member 82 may be configured as shown in FIGS. 1, 2 and 4. Nevertheless, the anchor member 82 may be configured otherwise to simply provide mechanical coupling to the attachment seal 14.

A method of mitigating retraction of a retractable needle safety syringe 10, the syringe comprising a syringe body 12, an attachment seal 14, a plunger assembly 16, a variable vacuum compartment 18, a shaft brake 20, and a ram member 22, the syringe body 12 defining opposing top and bottom syringe body ends 26 and including a syringe cavity 28, the attachment seal 14 defining a shaft orifice 30 and being attached to the top syringe body end 24, the plunger assembly 16 including a plunger shaft 32 and a piston 34, the plunger shaft 32 defining opposing top and bottom shaft ends 38, the plunger shaft 32 being disposed through the shaft orifice 30 in the syringe cavity 28, the piston 34 being disposed at the bottom shaft end 38, the plunger being slidably engaged with the syringe body 12 within the syringe cavity 28, the variable vacuum compartment 18 being disposed within the syringe cavity 28 between the piston 34 and the attachment seal 14, the variable vacuum compartment 18 being operative to provide a vacuum force 40 on the plunger shaft 32 directed from the bottom syringe body end 26 toward the top syringe body end 24 with the vacuum force 40 increasing upon movement of the piston 34 toward the bottom syringe body end 26, the shaft brake 20 being attached to the top syringe body end 24 and being operative to frictionally engage the plunger shaft 32 to provide first and second frictional forces 44 in opposition to the vacuum force 40, the first frictional force 42 being exerted upon the plunger shaft 32 prior to the piston 34 reaching the bottom syringe body end 26, the ram member 22 being attached to the top shaft end 36 and being formed to engage the shaft brake 20 upon the piston 34 reaching the bottom syringe body end 26, the shaft brake 20 exerting the second frictional force 44 upon the plunger shaft 32 in response to the engagement of the ram member 22 with the shaft brake 20, the second frictional force 44 being less than the first frictional force 42. The method comprises (a) exerting the first frictional force 42 upon the plunger shaft 32 in opposition to the vacuum force 40 prior to the piston 34 reaching the bottom syringe body end 26; (b) engaging the ram member 22 with the shaft brake 20; and (c) exerting the second frictional force 44 upon the plunger shaft 32 in opposition to the vacuum force 40 in response to the engagement of the ram member 22 with the shaft brake 20. In an embodiment, with the syringe including a needle 46, a further step in the method may include automatically retracting the needle 46 to a position within the syringe cavity 28.

In accordance with another aspect of the present method, the shaft brake 20 may define a body perimeter 60 and include an aperture 62 and a bridge 64, the aperture 62 being disposed within the shaft brake 20 and being operative to frictionally engage the plunger shaft 32, the bridge 64 defining the bridge width 66 extending radially from the aperture 62 toward the body perimeter 60, the shaft brake 20 being operative to exert the second frictional force 44 upon the plunger shaft 32 in response to an increase in bridge width 66, the bridge width 66 increasing in response to the engagement of the ram member 22 with the shaft brake 20, and step (b) of the method may further include: increasing the bridge width 66 in response to engagement of the ram member 22 with the shaft brake 20. Step (b) may also further include: severing the bridge 64 in response to engagement of the ram member 22 with the shaft brake 20. The severing may be done with a sharp edge disposed upon the ram member 22. Alternatively, the severing may be done utilizing a tool disposed on or incorporated into the bridge 64 itself, with the ram member 22 merely providing actuating the tool's severing of the bridge 64. In this regard, the bridge 64 may be variously configured to facilitate the severance thereof. The properties of the material used to fabricate the bridge 64 may also be manipulated as desired. For example, the bridge 64 may be fabricated from a brittle material that may sever or break upon engagement with the ram member 22.

In accordance with another aspect of the present method, the shaft brake 20 may further include a shoulder 70 being disposed upon the shaft brake 20 and protruding upwardly from the shaft brake 20 opposite the syringe body 12, the ram member 22 including a shoulder press 72 being sized and configured to engage the shoulder 70 upon the piston 34 approaching the bottom syringe body end 26, the bridge width 66 increasing in response to the engagement of the shoulder press 72 with the shoulder 70, and step (b) of the method may further include: engaging the shoulder press 72 with the shoulder 70 and deforming the bridge 64 to increase the bridge width 66. The engagement of the shoulder press 72 with the shoulder 70 may be done as shown in FIG. 2, with the shoulder press 72 being oriented at an angle relative to the thumb platform 52, and the shoulder 70 being configured to substantially mate with the shoulder press 72. Other various designs and configurations may also be implemented.

According to another implementation of the present method, the syringe may further include a needle 46 being removably mounted to the bottom syringe body end 26 and extending therefrom opposite the top syringe body end 24, the piston 34 including a punch 48 to engage the needle 6 upon the piston 34 reaching the bottom syringe body end 26, the piston 34 being operative to remove the needle 46 into the syringe cavity 28 upon exertion of the vacuum force 40 upon the plunger shaft 32, and the method may further include the steps of: engaging the needle 6 with the punch 48; and automatically removing the needle 46 into the syringe cavity 28.

This description of the various embodiments of the present invention is presented to illustrate the preferred embodiments of the present invention, and other inventive concepts may be otherwise variously embodied and employed. The appended claims are intended to be construed to include such variations except insofar as limited by the prior art. 

1. A retractable needle safety syringe with mitigated retraction, the syringe comprising: a syringe body defining opposing top and bottom syringe body ends and including a syringe cavity; an attachment seal defining a shaft orifice and being attached to the top syringe body end; a plunger assembly including a plunger shaft and a piston, the plunger shaft defining opposing top and bottom shaft ends, the plunger shaft being disposed through the shaft orifice in the syringe cavity, the piston being disposed at the bottom shaft end, the plunger being slidably engaged with the syringe body within the syringe cavity; a variable vacuum compartment being disposed within the syringe cavity between the piston and the attachment seal, the variable vacuum compartment being operative to provide a vacuum force on the plunger shaft directed from the bottom syringe body end toward the top syringe body end with the vacuum force increasing upon movement of the piston toward the bottom syringe body end; a shaft brake being attached to the top syringe body end and being operative to frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted upon the plunger shaft prior to the piston reaching the bottom syringe body end; and a ram member being attached to the top shaft end and being formed to engage the shaft brake upon the piston reaching the bottom syringe body end, the shaft brake exerting the second frictional force upon the plunger shaft in response to the engagement of the ram member with the shaft brake, the second frictional force being less than the first frictional force.
 2. The syringe of claim 1 wherein the first frictional force has an associated first normal force.
 3. The syringe of claim 1 wherein the second frictional force has an associated second normal force.
 4. The syringe of claim 1 wherein the shaft brake substantially disengages from the plunger shaft upon engagement of the ram member with the shaft brake.
 5. The syringe of claim 1 wherein the shaft brake defines a body perimeter and includes an aperture and a bridge, the aperture being disposed within the shaft brake and frictionally engaging the plunger shaft, the bridge defining a bridge width and extending radially from the aperture toward the body perimeter, the shaft brake being operative to exert the second frictional force upon the plunger shaft in response to an increase in bridge width, the bridge width increasing in response to the engagement of the ram member with the shaft brake.
 6. The syringe of claim 5 wherein the ram member at least partially severs the bridge to increase the bridge width.
 7. The syringe of claim 5 wherein the shaft brake further includes a release member being disposed upon the shaft brake, the bridge width increasing in response to the engagement of the ram member with the release member.
 8. The syringe of claim 7 wherein the release member is a shoulder protruding upwardly from the shaft brake opposite the syringe body, and the ram member includes a shoulder press being sized and configured to engage the shoulder upon the piston approaching the bottom syringe body end, the bridge width increasing in response to the engagement of the shoulder press with the shoulder.
 9. The syringe of claim 8 wherein the bridge width increases upon deformation of the bridge in response to engagement of the shoulder press with the shoulder and continued movement of the piston toward the bottom syringe body end.
 10. The syringe of claim 8 wherein the brake body defines a body thickness and the bridge defines a bridge thickness, the bridge thickness being less than the body thickness, the bridge being operative to deform in response to the engagement of the shoulder press with the shoulder.
 11. The syringe of claim 7 wherein the bridge comprises a non-continuous slit including a hinge element, and the bridge width increases upon deformation of the hinge element in response to engagement of the shoulder press with the shoulder and continued movement of the piston toward the bottom syringe body end.
 12. The syringe of claim 1 wherein the shaft brake is formed to include an anchor member being disposed upon the shaft brake, the anchor member being operative to mechanically couple the shaft brake to the attachment seal.
 13. The syringe of claim 1 further including a needle being removably mounted to the bottom syringe body end and extending therefrom opposite the top syringe body end, the piston including a punch to engage the needle upon the piston reaching the bottom syringe body end, the piston being operative to remove the needle into the syringe cavity upon exertion of the vacuum force upon the plunger shaft.
 14. A method of mitigating retraction of a retractable needle safety syringe, the syringe comprising a syringe body, an attachment seal, a plunger assembly, a variable vacuum compartment, a shaft brake, and a ram member, the syringe body defining opposing top and bottom syringe body ends and including a syringe cavity, the attachment seal defining a shaft orifice and being attached to the top syringe body end, the plunger assembly including a plunger shaft and a piston, the plunger shaft defining opposing top and bottom shaft ends, the plunger shaft being disposed through the shaft orifice in the syringe cavity, the piston being disposed at the bottom shaft end, the plunger being slidably engaged with the syringe body within the syringe cavity, the variable vacuum compartment being disposed within the syringe cavity between the piston and the attachment seal, the variable vacuum compartment being operative to provide a vacuum force on the plunger shaft directed from the bottom syringe body end toward the top syringe body end with the vacuum force increasing upon movement of the piston toward the bottom syringe body end, the shaft brake being attached to the top syringe body end and being operative to frictionally engage the plunger shaft to provide first and second frictional forces in opposition to the vacuum force, the first frictional force being exerted upon the plunger shaft prior to the piston reaching the bottom syringe body end, the ram member being attached to the top shaft end and being formed to engage the shaft brake upon the piston reaching the bottom syringe body end, the shaft brake exerting the second frictional force upon the plunger shaft in response to the engagement of the ram member with the shaft brake, the second frictional force being less than the first frictional force, the method comprising: a. exerting the first frictional force upon the plunger shaft in opposition to the vacuum force prior to the piston reaching the bottom syringe body end; b. engaging the ram member with the shaft brake; and c. exerting the second frictional force upon the plunger shaft in opposition to the vacuum force in response to the engagement of the ram member with the shaft brake.
 15. The method of claim 14 wherein the shaft brake defines a body perimeter and includes an aperture and a bridge, the aperture being disposed within the shaft brake and being operative to frictionally engage the plunger shaft, the bridge defining a bridge width and extending radially from the aperture toward the body perimeter, the shaft brake being operative to exert the second frictional force upon the plunger shaft in response to an increase in bridge width, the bridge width increasing in response to the engagement of the ram member with the shaft brake, and step (b) of the method further includes: a. increasing the bridge width in response to the engagement of the ram member with the shaft brake.
 16. The method of claim 14 wherein step (b) further includes: a. severing the bridge in response to the engagement of the ram member with the shaft brake.
 17. The method of claim 14 wherein the shaft brake further includes a shoulder being disposed upon the shaft brake and protruding upwardly from the shaft brake opposite the syringe body, and the ram member includes a shoulder press being sized and configured to engage the shoulder upon the piston approaching the bottom syringe body end, the bridge width increasing in response to the engagement of the shoulder press with the shoulder, and step (b) of the method further includes: a. engaging the shoulder press with the shoulder; and b. deforming the bridge to increase the bridge width.
 18. The method of claim 14 wherein the syringe further includes a needle being removably mounted to the bottom syringe body end and extending therefrom opposite the top syringe body end, the piston including a punch to engage the needle upon the piston reaching the bottom syringe body end, the piston being operative to remove the needle into the syringe cavity upon exertion of the vacuum force upon the plunger shaft, the method further including the steps of: a. engaging the needle with the punch; and b. automatically removing the needle into the syringe cavity. 